Forest Genetics Team

Genetic structure and processes of plant populations

Involves genetic diversity and processes at a variety of spatial and temporal scales are a major determinant of the ability of plant populations to adapt to changing environments and human values, and, thus, play a key role in forest health and productivity. Genetic structure and processes remain poorly described and understood for many plant species, including commercially important forest tree species, keystone species important in landscape restoration, and threatened or sensitive species of management concern.

Projects:

Genecology
Conservation Genetics
Taxonomy and Systematics

1.1 Genecology

The discipline of genecology is defined as the study of intraspecific variation and genetic composition as it relates to environment. Past research on forest genecology by the Team has been directed at describing genetic diversity in natural populations of economically important forest species, and relating levels of observed diversity to environmental variables, inferred historical events, and reproductive (mating) systems. In these studies, morphological and phenotypic variation is examined from defined populations through the use of common garden studies, an approach that allows variation to be divided into genotypic (heritable) and environmental components. Results from such studies permit inference into the distinctiveness of populations across the varied landscape of the Pacific Northwest Region. These inferences can be used to create seed movement guidelines, advanced generation strategies for plant breeding programs, gene conservation guidelines, and predictions for mitigating the impact of global climate change on forest communities. In the past, these studies have been conducted on a variety of valuable species, including Douglas-fir, ponderosa pine, western hemlock, western red cedar, sugar pine, western white pine, lodgepole pine, noble fir, red fir and Sitka spruce. Continuing genecological studies of economically important forest trees include Douglas-fir, ponderosa pine, western larch, and red alder

Genecological studies have recently been initiated by the Team for ecologically important species, mostly in response to the growing demand for seed transfer guidelines for native and sensitive plant species. An increasing number of native species are being used in landscape restoration (Booth and Jones 2001), and demand for these resources far exceeds availability. Accordingly, these species are becoming subject to increasing genetic manipulation through human-mediated selection, not only with regard to seed transfer (e.g., translocation of “native species” into new, “alien” environments), but also during the process of seed collection, increase and transplantation. Studies are presently being conducted on bitterbrush (Purshia tridentata) and wild blue rye (Elymus glaucus), and may be expanded to include threatened and endangered species.

Team Principal Investigators: Brad St.Clair and Randy Johnson

Collaborators: Frank Sorensen (retired PNW Genetics Team); Robert Westfall (PSW Station); Paul Berrang (NFS); Vicky Erickson (NSF); Willamette Valley Ponderosa Pine Conservation Association; Weyerhaeuser Company.

Benefits: Knowledge derived from genecological studies will provide managers and policy makers with sufficient background to make informed decisions affecting wood product sustainability, forest health, biological diversity, habitat restoration, and the evolutionary potential of forest species. Results from these studies provide a benchmark from which to evaluate the impact of disturbance regimes and human-mediated manipulation. Guidelines for seed movement, breeding strategies and ecological restoration will help ensure the success of rehabilitation strategies by providing plants that are well-adapted to the highly variable forest lands contained within the Pacific Northwest Region.

1.2 Conservation genetics

Research activities in conservation genetics will focus on characterizing the genetic status of plant populations of management concern, including threatened, endangered and sensitive (TES) and survey and manage (SM) species. Genetic characterization for sensitive species follows well established guidelines (Moritz et al.1995, Hamrick and Godt 1996), considering the magnitude and pattern of neutral marker diversity in threatened populations relative to widespread populations or sister species. Data will be used to predict mode of reproduction (sexual versus clonal), outcrossing rates, and the impact of isolation on inbreeding rates. Emphasis will be given to polyploid plants, which account for up to 70% of flowering plants, but which present unique (often insurmountable) challenges for genetic characterization. For example, research is presently being conducted on the SM grass Calamagrostis breweri (Brewer’s Alpine Reedgrass), which shows a narrow range in Oregon (only Mt. Hood and Mt. Jefferson) and a wider range in California. This plant exhibits two ploidy levels (tetraploid and hexaploid), which prompted botanists to divide this rare species into two highly restricted species (along chromosomal lines –Wilson and Gray 2002). C. breweri represents a useful model to evaluate new genetic marker technologies and analytical approaches for characterizing genetic diversity in variable polyploid plants. Ultimately, our work will elucidate the primary mode of reproduction for C. breweri, the frequency of chromosomal change within populations, the extent of differentiation within and among sites in Oregon and California, and the validity of the taxonomic treatment of Wilson and Gray (also see sect. 1.3). Once resolved, these approaches will be easily applied to other polyploid species of management concern across the PNW region.

In the future, similar studies will be conducted on TES and SM species that face extinction due to genetic assimilation through hybridization (Wolf et al., 2001). These studies will identify narrow endemics that demonstrate contact with widespread native species, or with introduced alien species (e.g., native Potentilla breweri and P. villosa versus introduced P. recta). Molecular genetic surveys will allow us to estimate the frequency of introgressive hybridization between rare and widespread plants, and to determine whether such processes pose an extinction risk for rare endemic species.

Team Principal Investigator: Richard Cronn

Collaborators: Aaron Liston, (Oregon State University); Marty Stein (Mt. Hood NF); Jenny Lippert and Mike Roantree (Willamette NF); Peggy Moore (USGS Ecological Field Station, Yosemite NP); Jonathan Wendel (Iowa State University); Nan Vance (PNW Biology of Forest Plants Team)

Benefits: Determining the extant and pattern of genetic variation in rare plants will promote more informed management decisions with regard to species maintenance, population augmentation, and potential translocation. Research may identify unique variants that warrant greater protection; conversely, research may identify populations sufficiently homogeneous (e.g., clonal) that reductions in population size will not impact viability. Finally, evaluating the risks associated with hybridization in rare plant populations will lead to a greater awareness of how to effectively manage TES and SM species in ecological zones that include widespread congeners.

1.3 Taxonomy and systematics

Research activities in the area of taxonomy and molecular systematics will focus on resolving continuing questions regarding species identity of plants located within the PNW region. The specific status of a substantial number of plants within Oregon and Washington remains debated, many of which are species of concern (e.g., TES/SM) to land managers. Leaving these questions unresolved represents a potentially significant cost to management agencies, as putative “species” (or subspecies) may be granted special status that may not be required by the Endangered Species Act or the National Forest Management Act.

As identified above, the Team is presently studying the rare polyploid grass Calamagrostis breweri. Recent taxonomic surveys by Wilson and Gray (2002) suggest that C. breweri may need to be separated into two species, C. breweri (found only in Oregon and one location in N. California) and C. muiriana (restricted to the central Sierras of California). This change could make C. breweri sufficiently restricted as to warrant elevation from its present status (Region 6 Survey and Manage) to a more protective classification (e.g., Threatened or Endangered). The interpretation of Wilson and Gray is based primarily on inconclusive genetic data; therefore, their proposals are being re-evaluated using more appropriate genetic tools to determine whether their conclusions are sound. Similar studies are underway to evaluate the controversial Washoe pine (Pinus washoensis) of southern Oregon and northern California, a conifer that has been proposed for active conservation efforts on the basis of it’s specific status (Niebling and Conkle 1990), but which may represent a geographic race of more widespread species ponderosa pine (Lauria 1997). Finally, collaborative research is being initiated on systematic interrelationships of the 100 species attributed to the pine genus Pinus. The Forest Genetics Team is providing the expertise to adapt molecular genomics tools derived from loblolly pine to studies concerned with relationships between and within pine species. This study (submitted to National Science Foundation for additional funding; Liston and Cronn 2002) will enhance our understanding of interrelationships among pines worldwide, and provide a framework for testing species concepts of questionable pines (e.g., Pinus washoensis).

Team Principal Investigator: Richard Cronn

Collaborators: Aaron Liston (Oregon State Univ); David Gernandt (Centro de Investigaciones Biologicas, Mexico); David Neale (USFS PSW Station); John Syring and Rebecca Huot (OSU students).

Benefits: Research results will clarify the status of poorly described or controversial species definitions. Since the first step in identifying threats to rare and endemic plants is correctly taxonomic identification, this work has the potential to minimize redundancy in conservation efforts, and to help land managers focus resources on highly threatened species, rather than unique varieties and forms.

US Forest Service - Pacific Northwest Research Station
Last Modified:  Wednesday, 12 January 2011 at 01:25:29 EST